WO1998026265A2

WO1998026265A2 - Method and device for nondestructively testing fluid-filled containers for leaktightness

Info

Publication number: WO1998026265A2
Application number: PCT/EP1997/006580
Authority: WO
Inventors: Jürgen Wittekind; Gerhard Poss; Andreas Kuehnel
Original assignee: Boehringer Ingelheim Pharma Kg
Priority date: 1996-12-10
Filing date: 1997-11-26
Publication date: 1998-06-18
Also published as: EP1015865B1; DE59711778D1; AU5556398A; EP1015865A2; US6314796B1; JP2001513189A; CA2274595A1; DE19651208C2; ATE271216T1; WO1998026265A3; DE19651208A1

Abstract

The invention concerns a method and corresponding device for nondestructively testing fluid-filled containers for leaktightness. The containers (17) to be tested are held ready in an evacuated receptacle (2) which is connected to a vessel (1, 1a - 1d) in which a gas discharge can be carried out. When the volatile contents of the container are discharged by means of a leakage in a container, the brightness of the gas discharge is noticeably reduced with respect to the brightness in the initial situation when only the residual gas molecules in the air are present in the vacuum. This change in brightness, detected by light-sensitive sensors (9), is proportional to the concentration of the volatile substances, such that, on the basis of a calibration curve, an evaluation circuit (10) can immediately provide information about the concentration of the respective substances.

Description

Method and device for non-destructive

Leak test of containers filled with liquid

The invention relates to a method for non-destructive leak testing of containers filled with liquid. The invention further relates to a corresponding device for non-destructive leak testing of containers filled with liquid.

The need for leak testing of containers filled with liquid arises in many areas of technology, for example in the pharmaceutical sector. The container can then be the cartridge of a pharmaceutical packaging, in particular a cartridge for a propellant-free metering aerosol.

Cartridges of this type have so far been beyond an economical leak test.

The international patent application WO 91/14468 describes such a container for the propellant-gas-free application of a metered amount of a liquid medicament as a spray for inhalation use of the type. The solution of the drug is in an exchangeable storage container, which consists of a dimensionally stable outer container and a flexible inner container. A precisely metered amount of the active ingredient solution is conveyed from this storage container into a pumping chamber and from there atomized under high pressure through a small nozzle, the particles formed being inhaled by the patient. Suitable storage containers are described, for example, in European Patent 532,873. The advantage of this double-walled container is that the solution of the Medicinal product can be removed without air or gas bubbles getting into the inner container. The pressure equalization takes place in that the inner flexible container collapses, while the outer dimensionally stable container protects against mechanical damage. The outer container contains openings for pressure equalization. If large amounts of air or gas residues were to accumulate in the inner container, an accurate and reproducible individual dosage would no longer be guaranteed for each individual application. A leak in the inner container, the wall of which consists of a very thin extruded film, would result in gas and air bubbles being formed in the course of use and possibly a smaller amount of active ingredient solution being inhaled. In order to achieve the greatest possible safety, it is therefore necessary to check the containers filled with the highly effective pharmaceutical solution to determine whether there is a leak in the inner container.

Cartridges of this type have so far been beyond an economical leak test.

In principle, highly sensitive sensors such as, for example, the flame ionization detector or the photoionization detector are used to detect traces of volatile substances. However, these sensors are dependent on a gas atmosphere in which there is at least atmospheric pressure; direct measurement in a vacuum is therefore not possible. However, in order to be able to test the tightness of a container filled with a liquid, it must be placed in a vacuum so that a sufficient amount of volatile substance is available for detection in the event of a leak. Furthermore, none of the previously known sensors makes it possible to detect traces of water in a gas atmosphere at a pressure below atmospheric pressure. It is also known in gas analysis technology to examine the analysis gas by emission spectrometry by ionizing the analysis gas in an evacuated gas discharge space, the pressure of which is between 0.01 and 5 torr, by means of a constant high-frequency discharge, that is to say a plasma is generated, the light phenomenon being spectral is broken down and the intensities of the spectral lines characteristic of the ionized gases are measured photoelectrically (DE-Auslegeschrift 1 124 734). Similar methods and devices for gas analysis are shown in the essay by Koch et. al. "About a new method for spectral gas analysis", in Angewandte Chemie, 71, 1959, pages 545 to 549; GB 2 185 573 A; DE 195 05 104 AI; DE 1 087 832; US-A 3,024,745 and DE-OS 1,598,303.

However, these known methods and devices are based on the analysis of supplied analysis gas by means of a spectral analysis and not on the leak test of containers filled with liquid.

The invention has for its object to provide a method and an apparatus for non-destructive leak testing of containers filled with liquid, which can detect leakage with great accuracy and in a simple manner.

This problem is solved according to the invention for the method with the steps:

Holding the containers filled with liquid in a vacuum,

Operating a gas discharge in the vacuum,

Detection of the light emission from the gas discharge, and

Evaluate the light emission for changes due to a leak in the tested containers

Container ingredients. With regard to the device, the object is achieved according to the invention

a recipient in which a pressure which is lower than atmospheric pressure can be maintained and in which those to be tested

Containers of substances are kept ready, a gas discharge path in a connected with the recipient

Vessel and electrical devices for operating the gas discharge, a light-sensitive sensor arrangement for detecting the of the

Gas discharge emitted light, and an evaluation circuit for evaluating the emitted light

Changes due to a leak in the tested container's volatile container contents.

If there is a leak in the containers, a small amount of the contents of the container evaporates due to the vacuum, whereby the gas discharge operated between two electrodes experiences both a change in the brightness and a change in the spectral composition of the light emitted by the gas discharge due to these material traces . Although this effect is reminiscent of the known methods of atomic spectrometry, in which the light emission of elements from a plasma operated at high power at atmospheric pressure is used for the detection of these elements, the detection of compounds, in particular of organic compounds, is in a vacuum with them Atomic spectrometry method not possible. In addition, a leak test of containers filled with liquid under atmospheric pressure is practically not possible.

The methodology of atomic spectrometry is described, for example, in:

Hoffmann, HJ. , Röhl, R.: "Plasma Emission Spectrometry". Analytiker Taschenbuch Vol. 5, pp. 69-92, Springer-Verlag (1985), and

Brockaert, J.A.C. , Schickling, C, Bings, N.: "Microwave plasmas for atomic spectrometry - state of development and analytical applications". GIT Fachz. Lab. 4/96, pp. 323-327.

The influence of the volatile container contents on the light emission of the gas discharge is particularly clear if, according to one embodiment of the invention, the containers are kept ready and the gas discharge is operated at a pressure between 0.5 and 50 mbar, preferably at a pressure between 1 and 4 mbar .

According to a further feature of the invention, it is furthermore conducive to the leak test if the gas discharge is operated by high-voltage electrical energy which is fed in by means of electrodes or capacitively or inductively.

Particularly good results can be achieved if the gas discharge is operated with a high voltage, which can be a direct voltage or an alternating voltage with a frequency of 50 kHz to 100 kHz, preferably 30-40 kHz, or an alternating voltage> 100 kHz.

The light emission can be evaluated according to various criteria. One way according to a further development of the invention is that the reduction in the brightness of the light emitted by the gas discharge compared to the basic brightness with the mere presence of the residual gas molecules of the air is detected in a vacuum and this brightness change in conjunction with a corresponding, empirically determined calibration curve with regard to the concentration of the respective volatile container content is evaluated. Another way according to an embodiment of the invention is that the change in the wavelength of the light emitted by the gas discharge is detected and evaluated with respect to a statement about the type of volatile container ingredient.

Further design features of the invention, in particular with regard to the device according to the invention, are the subject of subclaims and result from the following description of exemplary embodiments shown in the drawings.

Show it:

Fig. 1 shows a first embodiment of an inventive

Device with a straight tube for the

Gas discharge path, Fig. La a modification with a U-shaped tube for the

Gas discharge path, Fig. Lb a modification with a coiled tube for the

Gas discharge path, and Fig. 2 shows a second embodiment of an inventive

Device with a coaxial tube system for the

Gas discharge line.

Fig. 1 shows a device for non-destructive leak testing of liquid-filled containers with a vessel in the form of a tube 1 made of a translucent material, for. B. quartz or glass. In this tube, a reduced pressure compared to atmospheric pressure, a vacuum, can be maintained. For this purpose, it is connected between a recipient 2 and a vacuum pump 3. The filled containers to be subjected to the leak test are introduced into the recipient 2 (and thus into the vacuum), in the case of Leaks (leaks) traces of the filled container contents also get into the vessel 1, in which they are then detected in the manner yet to be described.

Two high-voltage electrodes 4, 5 are inserted into the vessel 1, between which a gas discharge path 6 can be formed. A high-voltage source 7 is provided for operating the gas discharge path 6 and feeds high-voltage electrical energy into the gas discharge path via the electrodes 4, 5. The applied high voltage can be a direct voltage or a low-frequency alternating voltage or a high-frequency alternating voltage, it being shown that with increasing frequency the emitted brightness depends less on the remaining gas pressure in the tube. Frequencies in the range of 30-40 kHz have been shown to be particularly favorable since there is no interference radiation at these frequencies.

To limit the current flowing through the gas discharge, a series resistor 8 is connected into the circuit, which can also be formed by a choke coil or a transformer with a large magnetic stray field. Instead of the electrodes 4, 5 used, flat outer electrodes can also be provided.

Instead of using electrodes, the high-voltage electrical energy can also be fed capacitively or inductively into the gas discharge path.

The device according to the invention also has a light-sensitive sensor arrangement, a photosensor 9, for detecting the light emitted by the gas discharge. The photosensor can be, for example, a photoresistor, a photodiode or a photocell. The photosensor 9 is followed by an evaluation stage 10, which is used to evaluate the emitted light for changes due to the traces of the contents of the container. In the simplest case, the evaluation stage is a measuring instrument for measuring the brightness-dependent electrical signal from the photosensor. It can also be formed by a microprocessor.

If a high voltage is now applied to the electrodes 4, 5, the remaining gas molecules inside the tube between the electrodes are excited to glow in the form of a gas discharge at reduced pressure, the wavelength of the emitted light depending on the type of the remaining gas molecules or - im In the case of noble gases - the gas atoms are determined, while the brightness is determined by the pressure in the tube and the level of the electrical voltage.

This process itself has long been known and is widely used, for example, in neon sign tubes. However, the invention is based on the effect that both the brightness and the wavelength of the emitted light are significantly changed by traces of volatile compounds.

It has been shown that when volatile organic or inorganic substances escaping from a leak in the filled containers, even in the smallest quantities, the gas discharge significantly reduces the brightness compared to the brightness that occurs in the initial situation, if only the rest Gas molecules of the air in the tube 1 are present. This change in brightness is proportional to the concentration of the volatile container contents, so that a direct statement about the concentration of the respective substances can be made on the basis of an empirically created calibration curve. The change in brightness is accompanied by a change in the wavelength of the emitted light, so that statements about the type of volatile substances are also possible.

If air, ie predominantly nitrogen and oxygen, are in the vacuum as residual gas molecules, the gas discharge emits a reddish / bluish light; If, for example, traces of ethanol are now introduced into the vacuum, the light emission shifts to the short-wave range with a light blue color and a high proportion of radiation in the near UV range. If water traces get into the vacuum, the gas discharge takes on a dark red color with a radiation component in the IR range.

In both cases, the emission in the visible range is clearly reduced.

A photosensor 9, which is wavelength-independent in a wide range of the light spectrum, is preferably used to measure the changes in brightness of the emitted light. To detect a specific, predetermined substance, a photosensor 9 is expediently used, which has a specific sensitivity maximum at a specific wavelength, which is matched to the type of substance. Several such photosensors with sensitivity maxima at different wavelengths can also be provided for the detection of different substances. The changes in wavelength can also be recorded using conventional relevant spectrally sensitive devices as evaluation stage 10 (or as part thereof).

Various design options exist for the vessel 1, into which the high-voltage electrodes 4, 5 are inserted, between which the gas discharge path 6 can be formed. The vessel can, as shown in Fig. 1, be a straight tube, but can also, as shown in Fig. La, a z. B. U-shaped curved tube la, which allows a particularly compact design.

According to the embodiment shown in FIG. 1b, the vessel can also be designed as a coiled tube 1b. In addition to a compact design, this embodiment enables particularly good utilization of the light emission if the light is used by means of an appropriate optics, for. B. a converging lens 11 is bundled in front of the photosensor 9.

FIG. 2 shows a further embodiment of the device according to the invention, which differs from FIGS. 1, 1a and 1b in particular by a fundamentally different design of the vessel 1 and the gas discharge path 6. The same parts are provided with the same reference numerals. In the device according to FIG. 2, the vessel 1 consists of two tubes lc, ld arranged coaxially one inside the other, which are cemented in a common metal flange 11 and of which the outer tube is closed at its free end and a fused-in electrode at the closed end 4 wears; the counter electrode 5 of FIG. 1 is formed by the metal flange 11 in this case.

The outer glass tube is closed by two spherical ground parts 12 and 13, of which part 13 carries electrode 4. The ground sections are sealed with an elastomer sealing ring 14, so that the usual grinding lubricants can be dispensed with.

The two spherical ground parts are pressed together in a vacuum-tight manner by a cap-like holder 15.

The gas stream pumped out by means of the vacuum pump 3 (not shown) initially flows through the inner tube 16, which additionally flows into a tube Threaded screw sleeve 16 is cemented, is deflected at the ball joint part 13 forming the closure, flows through the outer tube 1c back into the metal flange 11 and from there reaches the vacuum pump 3.

If, for example, small amounts of leakage are now emitted into the vacuum from the filled container 17 to be checked for leaks, this leads to the change in light emission described, which is detected by the photosensor 9 and supplied to the measuring device 10 as an electrical measured variable.

The measuring device 10 can also be replaced by a comparator which compares the electrical measured variable of the photosensor 9 with a predetermined setpoint value and in this way makes an automatic decision about the test process. This also applies to the embodiment according to FIG. 1.

The described embodiment according to FIG. 2 advantageously allows the device to be designed very compactly, so that the installation, for. B. is favored in a machine. In addition, it is possible to disassemble the measuring section for cleaning purposes with little effort.

An improvement in the light yield can be achieved if the side of the vessel facing away from the photosensor 9 is mirrored or if a separate mirror 12 is attached to this side, as is shown by way of example in FIG. Of course, these measures can also be applied accordingly to the other vessel shapes according to FIGS. 1, 1b and 2.

The detection sensitivity of the method according to the invention is to be shown on the basis of two examples presented below. In example 1, ethanol, in example 2 water, is metered into vessel 1. At a pressure of 2 mbar, a voltage of 2.5 kV and a Series resistance of 270 kΩ, the photometer signal in the initial state (only nitrogen and oxygen molecules as residual gas in a vacuum) is 9.7 V (idle signal).

In the tables given for the two examples, the absolute value of the photometer signal and the signal distance to the idle signal, i.e. the decrease in brightness.

You can see a significant decrease in brightness with increasing substance concentration.

Example 1:

Example 2:

The above-described method for non-destructive leak testing of containers filled with liquid and the associated device are particularly suitable for routine testing as part of the filling of the containers. The method according to the invention and the associated device are particularly suitable for routine leak testing of containers to be filled in large numbers. For example, automated multiple stations or larger test chambers can be set up as recipient 2 to accommodate several containers. Corresponding devices, which can also be evacuated, are known in principle from the prior art and can be readily adapted to the device in which the method according to the invention is carried out, that is to say by appropriately designing the connection of the recipient 2 to the gas discharge vessel 1 or la to ld.

Claims

claims

1. A method for the non-destructive leak test of containers filled with liquid, comprising the steps:

Keep the liquid-filled containers in one

Vacuum,

Operating a gas discharge in the vacuum,

Detection of the light emission from the gas discharge, and

Evaluate the light emission for changes by a

Volatile leakage in the tested containers

Container ingredients.

2. The method according to claim 1, characterized in that the holding of the containers and the operation of the gas discharge takes place at a pressure between 0.5 and 50 mbar, preferably at a pressure between 1 and 4 mbar.

3. The method according to claim 1 or 2, characterized in that the gas discharge is operated by high-voltage electrical energy which is fed by means of electrodes or capacitively or inductively.

4. The method according to claim 3, characterized in that the gas discharge is operated with a high voltage, which is a DC voltage, or an AC voltage with a frequency of 50 kHz to 100 kHz, preferably from 30-40 kHz, or an AC voltage> 100 kHz .

5. The method according to any one of claims 1 to 4, characterized in that the reduction in the brightness of the gas discharge emitted light, compared to the basic brightness when only the residual gas molecules of the air are present in a vacuum, and this change in brightness is evaluated in conjunction with a corresponding empirically determined calibration curve with regard to the concentration of the respective volatile container constituent.

6. The method according to any one of claims 1 to 5, characterized gekennezichnet that the change in the wavelength of the light emitted by the gas discharge is detected and evaluated with respect to a statement about the type of volatile container ingredient.

7. The method according to any one of claims 1 to 6 for testing cartridges for a friction gas-free aerosol with an exchangeable storage container containing the medicament, which consists of a dimensionally stable outer container and a flexible inner container to be tested for leaks.

8. The method according to any one of claims 1 to 7, characterized in that the leak test is carried out as a routine test in the context of filling the containers in large quantities.

9. The method according to claim 8, characterized in that several containers are kept ready in the vacuum.

10- Device for the non-destructive leak test of containers filled with liquid, with:

a recipient (2) in which a pressure which is lower than atmospheric pressure can be maintained and in which the containers to be tested are kept ready, a gas discharge path (6) in a vessel (1, la - ld) connected to the recipient (2) and electrical devices (4, 5, 7, 8) for operating the gas discharge,

a light-sensitive sensor arrangement (9) for detecting the light emitted by the gas discharge, and

an evaluation circuit (10) for evaluating the emitted light for changes due to a leak in the tested containers volatile container contents.

11. The device according to claim 10, characterized in that the electrical devices (4, 5, 7, 8) for operating the gas discharge have a high voltage source (7) in which high-voltage electrical energy can be generated by means of electrodes (4, 5) or can be fed capacitively or inductively into the gas discharge path (6).

12. The apparatus according to claim 11, characterized in that the high voltage is a DC voltage or an AC voltage with a frequency of 50 kHz to 100 kHz, preferably from 30-40 kHz, or an AC voltage of> 100 kHz.

13. Device according to one of claims 10 to 12, characterized in that the light-sensitive sensor arrangement (9) and the evaluation circuit (10) are designed so that changes in brightness and / or changes in the wavelength of the emitted light can be detected and evaluated.

14. The apparatus according to claim 13, characterized in that for measuring the changes in brightness of the emitted light as a photosensitive sensor arrangement (9) in a wide range of the light spectrum, wavelength-independent photosensor, such as photoresistor, photodiode or photocell, is provided.

15. The apparatus of claim 13 or 14, characterized in that a photosensor (9) is provided as a light-sensitive sensor arrangement with a specific sensitivity maximum at a certain wavelength, the sensitivity maximum being determined by the type of the substance to be detected.

16. The device according to one of claims 10 to 15 with feeding the high voltage via electrodes, characterized in that the vessel with the gas discharge path is formed from a tube system which consists of two or more tubes (lc, ld) which are arranged coaxially one inside the other , such that one side of the tubes is sealed in a metal flange (11) which also serves as the first electrode (5), while the other side of the outer tube (lc) is closed with two spherical ground parts (12, 13) from some of which carry the second electrode (14).

17. The device according to any one of claims 10 to 16, characterized in that the recipient (2), in which the containers to be tested filled with liquid are kept ready, is an evacuable automated multiple station for receiving several containers within the scope of a routine leak test of large quantities.

18. Device according to one of claims 10 to 16, characterized in that the recipient (2), in which the containers to be tested filled with liquid are kept ready, is an evacuable large test chamber for receiving several containers as part of a routine leak test of large quantities.